Pyrolytic conversion system

ABSTRACT

A rotary, continuous pyrolytic conversion system converts solid hydrocarbons into gases, liquid hydrocarbons and char by pyrolyzing feed stocks including: plastic waste, tires and plastic from automobile shredding operations; containers and trays of styrofoam and other plastic materials such as used in &#34;fast food&#34; restaurants; rubber; leather; tires; garbage; sewage sludge; coal; oil shale; broken asphalt and the like. These materials are preferably shredded and kinds thereof having different melting points are mixed to facilitate movement of the feed stock through the converter without clogging. Preferably, the materials are baled and injected into the converter where they are severed as they are injected. The materials are fed by gravity from the input end of a converter drum to the discharge end thereof; the input end being elevated above the discharge end. The converter drum is contained within an outer drum which is in substantially air-tight relationship with the injector for the bales and with a discharge chute for the solid products of pyrolysis. A casing around the outer stationary drum defines an oven chamber which is heated by combustion products, from a burner providing a heat source, which circulate in heat exchange relationship with a matrix of fins extending into the oven from the stationary outer drum. A rod extends into the injection end of the converter drum for supporting scrapers against the inner periphery of the converter drum. A crusher bar is carried in the drum at the discharge end thereof and crushes the solid products which consists of char (mostly carbon black), metals and other non-organic materials. A chute containing water receives the pulverized discharge product and balances the pressure in the converter to maintain an air-tight seal therein. A second pyrolysis reactor may receive the solid pyrolysis products and be operative at higher temperature than the first converter to destroy chlorinated hydrocarbons. To assist in such destruction, lime may be injected into the first converter. A plurality of converters may be operated in parallel and utilize common equipment for cleaning the product gases released upon pyrolysis and to supply them to the burners of each of the reactors. Flue gases from the oven chambers of one of the plurality of converters may be supplied to the burner of the next converter for preheating gases for combustion therein.

This is a division of application Ser. No. 494,256, filed Mar. 14, 1990,now U.S. Pat. No. 5,082,534.

DESCRIPTION

The present invention relates to pyrolysis conversion systems (methodsand apparatus), and particularly to systems utilizing rotary drumpyrolytic converters.

The invention is especially suitable for use in the pyrolytic conversionof solid hydrocarbons into gases, liquid hydrocarbons and char by thepyrolysis of various feed stocks, such as the tires and plastic wasteresulting from shredding of junked automobiles. The system is alsoadapted for pyrolyzing other waste, such plastic containers and traysfrom fast food restaurants, garbage, sewage sludge, coal, oil shale,broken asphalt and the like which may be comminuted and mixed to providethe feed stock for the converters of the system.

Pyrolytic converters as have heretofore been provided have requiredconveyers, augers, or carts for moving the materials to be pyrolyzedthrough the converter. Practical and reliable operation of pyrolysisconverters has not been obtained because such devices must operate athigh temperatures, for example, exceeding 1,000° F. Also the material tobe processed and the products of pyrolysis, solids, liquids and gasesmust be introduced and discharged without adversely affecting theintegrity of the converter, so that air cannot enter the converter andinterfere with the pyrolysis process or engender dangerous, explosiveconditions. Pyrolysis reactions also result in the formation of gums andclumps which interfere with the transfer of heat to the material beingpyrolyzed as well as with the discharge of the products of pyrolysis.

The solution of the foregoing problems without introducing complexitiesin design and operation which would affect the reliability andmaintainability of the system is the principal feature of the invention.The invention also addresses the need for flexibility in the capacity ofthe system and makes it possible to increase the capacity of the systemwithout extensive modifications.

Accordingly, it is the principal objective of the present invention toprovide an improved pyrolytic conversion system.

It is another object of the present invention to provide an improvedpyrolytic converter utilizing a rotary drum.

It is a still further object of the invention to provide an improvedpyrolytic conversion system capable of processing various types ofhydrocarbon containing materials and which is reliable and maintainable.

It is a still further object of the present invention to provide animproved pyrolytic conversion system which can be expanded in capacitywithout extensive modification.

It is still another object of the invention to provide an improvedpyrolytic conversion system capable of destroying environmentally unsafehydrocarbon materials, such PCB's.

It is a still further object of the present invention to provide animproved pyrolytic conversion system which is less complex in design andhas fewer moving parts than prior systems, and has essentially no movingparts within the converter drum thereof.

Briefly described, a pyrolytic conversion system in accordance with theinvention handles solid hydrocarbon containing materials. It utilizes aconverter drum having opposite ends; the first of which is elevatedabove the second. The drum also has an axis of rotation about which itis rotatable. There is an outer stationary drum disposed around theconverter drum. This stationary drum defines a chamber (which ismaintained substantially air-tight) within which the converter drum isdisposed. A casing is disposed around the outer drum and defines an ovenchamber. Means are provided for heating the oven chamber to maintain theconverter drum at a temperature sufficient to pyrolyze materials ofinterest. Means are provided which are in communication with the chamberformed by the outer drum, which are located near the first end of theconverter drum, for extracting product gases of pyrolyzation. Othermeans are disposed in essentially airtight relationship with the chamberformed by the outer drum, which are located near the second end of theconverter drum, for the discharge of the solid products of pyrolyzation.Means are provided which extend through the chamber formed by the outerdrum for injecting the materials to be treated into the first end of theconverter drum while essentially excluding air from the chamber formedby the stationary drum. Hot gases flow through the oven chamber and aretransferred, through the chamber formed by the outer drum, to theconverter drum. The hydrocarbon materials are motivated by gravity andthe rotation of the converter drum and move as they are being pyrolyzedfrom the first end to the second end where the solid products ofpyrolyzation are discharged, while the gaseous and volatile products areextracted near the first end of the converter drum. No conveyers, augersor other transports are used within the converter drum.

The foregoing and other objects, features and advantages of theinvention, as well as presently preferred embodiments thereof, willbecome more apparent from a reading of the following description inconnection with the accompanying drawings in which:

FIG. 1 is a side elevational view of a pyrolytic conversion systemembodying the invention;

FIG. 2 is a front (take from the left in FIG. 1) elevational view of thesystem shown in FIG. 1;

FIG. 3 is a rear elevational view of the system shown in FIG. 1;

FIG. 4 is a longitudinal cross-sectional view through the axis of theconverter drum with support structures removed to simplify theillustration;

FIG. 5 is an enlarged, longitudinal cross-sectional view showing theconverter drum, the outer drum and the casing providing the ovenchamber;

FIG. 6 is an end view taken along the line 6--6 in FIG. 5;

FIG. 7 is a sectional view taken along the line 7--7 in FIG. 5;

FIG. 8 is a sectional view taken along the line 8--8 in FIG. 5.

FIG. 9 is an end view taken along the line 9--9 in FIG. 5;

FIG. 10 is a sectional view taken along the line 10--10 in FIG. 5;

FIG. 11 is a fragmentary sectional view taken along the line 11--11 inFIG. 10;

FIG. 12 is a fragmentary sectional view taken along the line 12--12 inFIG. 11;

FIG. 13 is plan view of the roller assembly shown in FIGS. 11 and 12;

FIG. 14 is a bottom view of the roller assembly shown in FIG. 13;

FIG. 15 is a sectional view taken along the line 15--15 in FIG. 5;

FIG. 15a is an enlarged view of the spacer and support arrangement shownin FIG. 15, the view being taken along the line 15a--15a in FIG. 15;

FIG. 16 is a side elevation of the converter drum assembly partiallybroken away at the discharge end thereof;

FIG. 17 is a cross-sectional view taken along the line 17--17 in FIG.16;

FIG. 18 is a sectional view taken along the line 18--18 in FIG. 16;

FIG. 19 is an end view of the assembly shown in FIG. 16 taken along theline 19--19 in FIG. 16;

FIG. 20 is an enlarged fragmentary cross-sectional view of the driveshaft assembly at the discharge end of the converter drum, taken along avertical plane through axis of rotation of the converter drum;

FIG. 21 is a longitudinal cross-sectional view of the injector tubeassembly which is located at the inlet end of the converter drum;

FIGS. 22 and 23 are cross-sectional views taken along the line 22--22 inFIG. 21 and showing the injector tube bale receiving cover in open andclose positions respectively;

FIG. 24 is a sectional view along the line 24--24 in FIG. 21;

FIG. 25 is a side elevation of the discharge chute and conveyor assemblyof the of the system shown in FIGS. 1-4;

FIG. 26 is an end view of the assembly shown in FIG. 25 taken from theright as viewed in FIG. 25;

FIG. 27 is a plan view of the assembly shown in FIG. 25;

FIG. 28 is an enlarged, fragmentary cross-sectional view of the bottomof the discharge chute and the conveyor assembly which is shown in FIGS.25-27; the view being taken along the line 28--28 in FIG. 30;

FIG. 29 is an enlarged, fragmentary, sectional view of the portion ofthe assembly shown in FIG. 28, the view taken within the line 29--29 ofFIG. 28;

FIG. 30 is a sectional view taken along the line 30--30 in FIG. 28;

FIG. 31 is an enlarged view of FIG. 30 taken along the line 31--31 inFIG. 30;

FIG. 32 is an enlarged end view of one of the scraper bars of theconveyor assembly taken along the line 32--32 in FIG. 30;

FIG. 33 is an cross-sectional view of the condenser tank shown in FIGS.1-4 and one of the condenser tanks shown in FIG. 39, the section beingtaken along the line 33--33 in FIG. 35;

FIG. 34 is a side elevation of the condenser shown in FIG. 33;

FIG. 35 is a bottom view of the condenser shown in FIG. 33;

FIG. 36 is a cross-section taken along the line 36--36 of FIG. 38 of oneof the three final condensers shown in FIG. 39;

FIG. 37 is a side elevation of the condenser shown in FIG. 36;

FIG. 38 is a bottom view of the condenser shown in FIG. 36;

FIG. 39 is a schematic diagram of a multiple converter, pyrolyticconversion system embodying the invention; and

FIG. 40 is a side elevation of a pyrolytic conversion system utilizing asecondary pyrolytic converter at the discharge end of a first converter,the secondary converter being similar to the converter shown anddescribed in connection with FIGS. 1 to 38.

Referring to FIGS. 1-4 there is shown a pyrolytic converter system 10having a single pyrolytic converter 12. A plurality of such convertersmay be operated in parallel in an expanded system when greater capacityfor handling more feedstocks within a given period of time is required.A expanded system is shown schematically in FIG. 39 and will bedescribed hereinafter. The size of the converter 12 and other componentsof the system 10 also depends upon the desired feedstock handlingcapacity of the system. A small scale or pilot system may utilize aconverter 12 which is about 21.5 feet long and about 38 inches indiameter across the outside thereof. A full scale system may typicallyhave a converter 12, 40 feet long and of a outer diameter of about 114inches. All such dimensions are typical and approximate. It will beappreciated that the system may be scaled to meet specified capacity andother operating and performance requirements.

The feedstocks are prepared in a storage and preparation section of thesystem 10 which is not shown in the drawings. Conventional shredders,mixers and balers may be used to form the feedstock into comminutedpieces. The system preferably uses mixtures of different types ofmaterials for its feedstocks. Each type which is mixed has a differentmelting point. This mixture of materials with different melting pointsfacilitates smooth movement of the feedstock through the converter 12without clogging and gumming thereof, as pyrolysis proceeds.

The drawings show a typical bale 14. These bales are cylindrical andapproximately the same diameter as an injection tube 18, which is partof the apparatus for introducing the feedstock into the converter 12.Another part of the introduction apparatus is a hopper 16. In a pilotsystem, the bales may be approximately 8 inches in diameter and 20inches long. A typical full scale system may utilize bales 36 inches indiameter and 48 inches long. The injection tube 18 may be five to sevenfeet long from the hopper 16 to the end thereof which is located insidethe converter 12. The tube 18 may be made in sections connected byflanges 20. The section of the tube 58 which enters the converter 12(see FIG. 4) may be of a material which is different from the rest ofthe tube 18 and which is more resistant to heat.

The converter 12, as shown in FIG. 4, has a rotatable inner drum 66 inwhich pyrolysis occurs. Around the inner drum 66 is a stationary,non-rotating outer drum 68. This outer drum is closed at its ends bybulkheads 157 and 158 which define an essentially air-tight chamberaround the rotating inner drum 66. The inner drum is rotated by a driveshaft assembly 22 having a sprocket 182 which is driven by an electricmotor through a gear box 183, an output sprocket 187 from the gear boxand an endless chain 185. The motor may be a one horse power (for apilot, small size converter) to ten horse power for a typical full scaleconverter. The output RPM may be approximately 1,800 and the gearreduction in the box 183 may be 900 to one or 1,800 to one. The driveshaft (102, FIG. 20) of the assembly 22 may be 2.375 inches in diameterfor the small scale converter to 4.5 inches in diameter for the fullscale converter. The drive shaft assembly is water cooled and isdescribed in greater detail in connection with FIG. 20.

The outer drum 68 is surrounded by a casing generally indicated byreference numeral 52 and shown in greater detail in FIGS. 15 and 15A.This casing defines an oven chamber around the outer drum through whichcombustion gases from a burner heat source 26 circulate. The burner 26is preferably a forced air type where combustion air is fed throughburners which burn product gases of pyrolysis during continuousoperation of the converter 12. Thus, the hot gases circulate through theoven chamber under pressure. On startup, other heating gases such aspropane may be used. The product gases of pyrolysis may be stored andused from storage, both on startup and during operation (see FIG. 39).Augmented, forced air may come from a gas turbine exhaust and the burner26 may be of the type used for auxiliary firing of gas turbine exhausts.Such burners are also known as duct burners and are available from COENCompany, Inc., 1510 Raulins Road, Burlingame, Calif. 94010. The airflows through the oven chamber to an outlet chimney or flue 24. Thisflue may be connected to scrubbing equipment or pass through a so-called"bag house" if desirable or necessary for environmental protectionpurposes. The gases from the flue 24 may be used to preheat or providehot combustion gases to the heater of a successive converter (instead ofa gas turbine exhaust) in a multiple converter system as shown in FIG.39.

The converter 12 and the injection tube 18 is supported on a framework48 resting on the ground, preferably on a concrete slab 50. Inasmuch asthe converter 12 can expand and contract with respect to the frameworkwhich supports it, the rear end of the converter 12 is mounted on aroller 28. The discharge of solid products of pyrolysis is throughopenings in the rear end of the rotating drum 66 and the outer drum 68via a chute 30. This discharge chute 30 is mounted on a conveyorassembly 34 so that it can move with respect to the assembly 34. Suchmovement is facilitated by a flexible pipe or bellows 32 which surroundsthe lower end of the discharge chute 30. The discharge chute 30 and theconveyor assembly is shown in FIGS. 27 through 32 which illustrates theconnection between the discharge chute 30, the flexible bellows pipe 32and the housing 82 of the conveyor assembly 34.

A seal is maintained at the discharge end of the converter in the chuteby virtue of the chute; the conveyor housing 82, and the bellows pipe 32being filled with liquid, preferably water. The height of the liquid issuch that a pressure is presented to the chamber defined by the outerdrum 68, which balances and maintains the pressure therein. A suitablepressure is slightly above atmospheric pressure (e.g. 5 PSIG). Thiswater level is indicated at 72.

The pressure in the product delivery chute 30 may be sensed by a sensor43 (FIG. 39) near the exit from the converter drum 66 and transmitted toa pressure regulator 45, located after the last condenser, whichcontrols or balances the pressure so that the weight of the residueinside the discharge chute is just enough to overcome the friction ofthe residue. In effect, the pressure inside the converter drum 66 israised enough to lower the water level inside the chute to within a fewinches of the bottom of the discharge chute (to 72B in FIG. 4).

The conveyor casing 82 is closed by conveyor top 206 (see FIGS. 28-32),except for a discharge chute 84 which delivers the solid products ofpyrolysis (principally char or carbon black) 38 to a conveyor 40. Theconveyor 40 carries the residue which is discharged to apparatus (notshown) for separation of ferrous, nonferrous metals and other inorganicmaterials and processing or refining of the carbon black. The balance ofthe discharge may be used for land fill.

The residue of pyrolysis consist mostly of this carbon black or char andalso contains ferrous and non-ferrous metals and other non-organicmaterials. Since these materials are discharged under water, they arequenched, cooled and cleaned of sulfur, ammonia, calcium chloride asthey are fed through the water by a roller chain conveyor 74 driven by adrive sprocket 76 and carried on support sprockets 78. The chainconveyor carries the scrapper blades 80 so that they scrap thedischarged products from the bottom of the conveyor housing 82 and carrythem up through the water bath to a level which is elevated above thetop level 72 of the water where they are discharged through the snout84.

An outlet for volatile gases released during pyrolysis of the feedstockis shown at 87 near the inlet end of the rotary drum 66. These gases arecarried by a delivery pipe 42 to a condenser 44. The pressure in thechamber defined by the outer drum is controlled by a pressure sensor 43connected to the pipe 42 adjacent to the outlet 87 which operates aregulator valve 45 via conventional control equipment (not shown). Theproduct gases are collected at a gas outlet pipe 46. They may becirculated through a series of tandem condensers as shown in FIG. 39.The non-condensable product gases are methane, propane, etc. Theseproduct gases are desirably used to fire the burner 26.

The condenser 44 is shown in greater detail in FIGS. 33 to 35.Generally, it is of the fluid bath type which has baffles 224 some ofwhich extend below the level of the bath and which establish a gasstream over and through the bath so as to cool and clean the impuritiesin the volatiles. Such impurities are carbon particles, ash, calciumchloride (a product of lime which, optionally, may be injected into theconverter to reduce the chlorine in certain plastics such as vinyls,PCBs, and alike, into calcium chloride). The bath also removes sulfurand ammonia. The petroleum or oil based volatiles condense and float onthe top of the water in the bath. These oils may be collected via avalved discharge pipe (not shown) near the top of one of the side wallsof the condenser 44. The temperature of the bath may be maintained bycirculating or recirculating cooled or chilled water.

The apparatus for introducing the feedstock bales or bags 14 utilizes ahydraulic cylinder 54 with a plunger 56 having a diameter approximatelyequal to the diameter of the tube 18. The term "bales" should be takento include bags. As shown in FIGS. 21 through 24, the portion of thetube 18 below the hopper 16 has a cover 194 hinged at 198. The cover isopened and closed by a hydraulic cylinder 196. When the cover is open, abale drops into the tube 18. Then the cover is closed as shown in FIG.3. The hydraulic cylinder 54 is then operated and the plunger 56 ramsthe bale toward the inlet end of the converter 12. Bales are rammed oneat a time. Since they are approximately the same diameter as the tube 18they form a seal as they are compressed. Air and water trapped in andbetween successive bales is exhausted through air bleed holes 192 andwater bleed holes 192A on the top and bottom of the tube 18 and adjacentto the hopper 16. As the bales enter the converter they are severed by aknife 60 attached to the end 58 of the injection tube 18 which islocated inside the rotary converter drum 66.

On start up of the system or in the event that maintenance is required,it is desirable to purge the system. To this end inlet valves 86 allowan inert gas, such as CO₂, to pass into the chamber defined by the outerdrum and through the outlet pipe 42. The purging gases are released viaan outlet valve 88.

The outer drum 68 is best illustrated in FIGS. 5 through 9, 15 and 15A.This drum as well as other parts of the converter 12 which are at hightemperatures are desirably made of stainless steel of the type andclass, capable of sustaining such temperatures, for example type 304 or316 stainless. The bulkheads 157 and 158 are plates which are connected,in the case of the bulkhead 157 to the inner end 58 of the injectiontube 18. There are radial gussets 92 on the outside of the rear bulkhead158 around a journal 106 (see also FIG. 20) through which the driveshaft 102 of the drive shaft assembly 22 passes. The space between thesegussets may be filled with insulating material, such as rock wool whichis also shown at 52. The bulkheads 157 and 158 and their associatedcomponents therefore provide part of the oven casing. As well as servingthe dual function of sealing the chamber in which the rotary drum islocated and pyrolysis reactions occur.

The outer drum has longitudinal fins 94 which direct the combustiongases heated by the heater, and which pass through the heat source inlet108, towards the outlet flue 24. These fins 94 are circumferentiallyspaced around the stationary outer drum 68. Between the longitudinalfins 94 (which also extend in the direction of the axis of rotation ofthe rotating converter drum 66) are spacer fins 96. These spacer fins 96are longitudinally spaced from each other in the direction of the axisof rotation of the converter drum 66. The spacers for example may be atthree foot intervals around the outside periphery of the stationaryouter drum. These spacers create turbulence in the forced draft of hotgases which circulates through the oven chamber. Such turbulenceenhances heat transfer from these hot gases to the outer drum, andthence to the chamber inside the outer drum 68, where the rotating drum66 carries the feedstocks undergoing pyrolysis.

The outer drum 68 may have a diameter of approximately 19.125 inches ina small scale (pilot) converter and a diameter of 80 inches in a fullscale converter. The converter drum 66 for a small scale (pilot)converter may be 17 inches in diameter, while in a full capacityconverter the diameter of the converter drum 66 may be 72 inches.

The support of the converter 12 on the frame 48 is provided by theroller 28 which extends under a wedge shaped support platform 49 havingan upper surface 29 which is parallel to the axis of rotation of theconverter drum and the drive shaft 102 (see FIG. 4). The lower surfaceis generally parallel to the surface of the ground or support pad 50 (ishorizontal). The inclination of the wedge therefore is approximatelyequal to the inclination of the axis of rotation of the converter drumwhich may be approximately 6°. In other words, the rear or discharge endof the converter drum and the inlet end of the converter drum are atdifferent elevations; the inlet end being higher than the discharge end.The discharge end of the converter drum 66 is supported by the driveshaft 102 which is in turn supported in bearings in a pillow blockresting on the rear support platform 49. This pillow block is shown at180 (see FIG. 20). The forward end of the converter drum 66 and theouter stationary drum are supported on roller assemblies 62.

The roller assemblies 62 are shown in greater detail in FIGS. 10 to 14.A wear ring 110 is welded around the converter drum near the forward orinlet end thereof. Rollers 112 are rotatably mounted between thrust ballbearings 114 on a carrier 116. The wear ring 110 rests on the rollers112. A plurality of roller assemblies are provided which arecircumferentially spaced apart. Hardened bushings 118 surrounds earsextending laterally from each roller 112. These bushings 118 journal therollers 112 in the carrier 116. The carrier is a rectangular block whichrests on an inner pipe 122 of a pipe assembly including the inner pipe122. This assembly contains an outer pipe 120 which is welded to aflange 126 and rests upon a blind flange 128. A shim disk 124 is locatedinside the outer pipe 120 under pipe 122, on the flange 128. Byselecting the thickness of this shim the converter drum 66 may beadjusted.

An adjustment to the inclination of the converter may be made byraising, (e.g., about 2° or lowering about 2°) the high end of the unit12 at the support frame 48. The floating lower end of the dischargechute 30 inside the bellows 32 allows for this 2° plus or minusadjustment.

Such adjustment will depend upon the nature of the feedstocks, since theangle of inclination of the converter drum determines the rate at whichthe feedstocks travel through the converter drum and their duration inthe drum. Different feedstocks may require different lengths of time ofpyrolysis in order to complete the pyrolysis reaction.

An inlet and an outlet for pipes 132 and 144 which respectively carrywater into and out of the chamber formed inside the inner pipe 122 areprovided for cooling each roller assembly 62. A drain plug 130 or adrain valve may be used to drain the water from the roller assembly.

The outer pipe 120 extends to the outer, stationary drum 68 and, withthe aid of gussets 136, supports the roller assemblies 62.

Referring to FIGS. 15 and 15A, the support for the oven casing 52 andthe design of the oven casing are shown in greater detail. The ovencasing has an inner shield or cover 138 and an outer shield or cover140. These shields are separated by spacers 144. The spacers 144 areconnected to support members 142 by being threaded therein. The spacersthemselves are secured by spacer bolts 146. The support members 142 areattached to different ones of the longitudinal spacer fins 194 on thestationary outer drum 68. Six support members are shown which are spacedapart 60° from each other circumferentially around the stationary drum68. The spaces between the shields 138 and 140 are desirably filled withinsulating material, such as rock wool.

In order to scrape material which may adhere to the inside periphery ofthe converter drum 66, a scraper assembly 64 is provided. This assemblyincludes a rod in a sleeve (not shown) which is welded to the upper(above the meridian through the axis of rotation of the converter drum)gussets 92 of the bulkhead 157. Scraper blades are yieldably connected,as by being mounted on springs (see FIG. 7) and engage the insideperiphery of the converter drum 66 above the meridian through its axisof rotation.

As shown in FIG. 5 and in greater detail in FIGS. 16-20, the converterdrum 66 has torque rods 90 which are circumferentially spaced at equalangular increments and extend between the end of the rotating converterwhich is defined by bulkheads 150 and 152. These bulkheads areinterconnected by gussets 156 which extend radially to the drive shaft102 and may be welded thereto. The bulkheads 150 and 152 are disks whichare also welded to the drive shaft 102. A ring or flange 154 extendslongitudinally between the bulkheads. The torque rods are preferablywelded to the ring 154 as well as to the gussets 156. The torque rodsextend into the rear end of the converter drum 66 and are welded to theinner periphery thereof. These torque rods 90 define gaps or openingsthrough which the solid products (residue) of pyrolysis reaction in theconverter drum fall into the discharge chute 30. The length of theseopenings defined by the rods 90 (in a direction along the axis ofrotation) may be nine inches in a small-scale pilot converter and twelveto eighteen inches in a full-scale converter. The torque bars themselvesmay be six in number in a small-scale converter and one inch indiameter. In a large-scale converter, twelve torque bars, two inches indiameter, may be used. The opening in the outer drum 68 faces theseopenings in the converter drum and may be nine inches by twelve inches(rectangular) for a small-scale converter and eighteen inches by sixteeninches for a full-capacity converter. The discharge chute 30 may berectangular where it meets the discharge opening. The duct work may varyto a circular cross-section from the rectangular cross-section in thelower part of the chute 30 where the bellows pipe 32 surrounds the chute30.

A preferably circular or octagonal crusher bar 70 having a length longerthan the torque bars 90 but not more than twice the length of the torquebars is disposed loosely in the discharge end of the converter drum 66.As the converter drum rotates (FIG. 8), the crusher bar 70 is picked upby the torque rods, elevated and then released, thereby crushing clumpsin the residue and pulverizing them into particles which fall downthrough the openings between the torque bars 90. The weight of thisresidue overcomes the pressure presented by the water in the dischargechute so that the residue drops through the discharge chute and thewater into the conveyor housing 82 (FIGS. 27-32) where a conveyor havingscraper blades 80 pick up the residue and carries it up to a dischargesnout 84.

In order to reduce the presence of chlorinated organic hydrocarbons inthe residue which is discharged from the converter drum 66, a source ofa reagent which reacts with chlorine in such hydrocarbons may beinjected in the inlet end of the converter drum. For such purpose, limemay be used which is injected via a control valve 98 through aninjection pipe 100 into the inlet end of the converter drum 66 below themeridian thereof (the generally horizontally disposed plane through theaxis of rotation of the drum 66). Calcium in the lime reacts with thechlorine of the chlorinated hydrocarbons to produce calcium chloridewhich is cleaned from the residue (mostly char) discharged via the waterbath in the conveyor housing 82 and the chute tube 30.

Referring more particularly to FIG. 20, there is shown the drive shaftassembly 22. The principal feature of this assembly is that it is watercooled so that it can operate reliably in the high temperatureenvironment of the converter 12. The drive shaft assembly includes thedrive shaft 102 and a journal 106. A thrust washer 104 is disposedbetween the bulkhead plate 152 at the rear end of the converter drum andthe bulkhead 158 at the rear end of the outer, stationary drum. Thejournal 106 defines a stuffing box containing high-temperature packing164 and a chamber where water is contained as it is circulated between awater inlet 160 and a water outlet 162.

The packing 164 is contained by a packing gland 166 which is also watercooled within a chamber thereof defined by a bellows 170. The bellows170 may be welded at the end thereof to the flange of the gland 166 andto a seal carrier 174. The welds are shown at 172. A seal 176,preferably of the Garlock type, extends around the drive shaft 102 inthe seal carrier 174. The water connection 168 is dead-headed. It may beconnected to a T-connector through which water circulates. Accordingly,there may be a convective flow of water which cools the seal and theshaft 102. The water is pressurized at the same pressure as the insideof the converter and the discharge chute; or slightly above to ensurethat no gases can escape through seal 164. A small water leak into theconverter can be tolerated. The shaft 102 also has a cavity 178 (a hole)bored therein which extends into the area of the journal 106. A jackshaft 186 extends rearwardly from the drive shaft 102 and is connectedthrough a swivel 188 which has a water inlet connection 190. Again, aT-connection for water circulating past the swivel may be provided toaccommodate convective flow of the water in the cavity 178. Alternately,a small pipe may be inserted through the swivel into the far end of thewater cavity 178 which forces cool water to the far end of the cavity,while discharging the warm water through the same swivel.

The pillow block, which supports the drive shaft and through which therear end of the converter 12 is supported, is shown at 180 and FIG. 20,and was discussed above. The shaft drive sprocket 182 is also shown inFIG. 20 keyed to the shaft by a key 184. This drive sprocket 182 isconnected via the chain 185 and sprocket 187 to the gear box 183 asshown in FIG. 3.

The discharge chute 30 and the conveyor assembly 34 were mentioned abovein connection with FIGS. 27-32. Referring again to these figures, itwill be seen that the upper end of the bellows pipe 32 is fixed to theouter periphery of the chute by gussets 200 and flanges 204 (FIG. 25 and26). A bleed-off valve to allow air to bleed from the bellows above thewater level therein is shown at 202. The bellows pipe is connected bybeing welded to a ring 206 which is spaced above the inverted end of thesides 208 of the conveyor housing 82. This inverted end is sandwichedbetween the ring 206 and a flange 210 around the bottom of the chute 30.As shown in FIG. 28, which illustrates the non-thermally expandedcondition and exemplary 6° slope of the converter 12 and FIG. 29 whichshows expansion by a displacement 212, it will be seen that the bellowspipe 32 enables movement of the discharge chute with respect to theconveyor housing 82 and accommodates such movement. Even in asmall-scale converter, the movement may be two and one-half inches dueto thermal expansion of the converter 12. Such movement is accommodatedby the bellows pipe arrangement which enables relative motion of thedischarge chute 30 with respect to the conveyor housing 82 whilemaintaining the liquid seal.

An underwater support sprocket 78, FIG. 30 for the roller chain 74 ofthe conveyor is carried on a shaft 213 by being keyed thereto. Thisshaft is journaled in stuffing boxes 216 on the side walls 208 of theconveyor housing 82. The shaft is journaled and supported in pillowblocks 214. The scraper blades 80 are carried on the chain 74. The endtips 218 of the blades 80 are bent up (FIG. 32) and in a forwarddirection in which the conveyor is moving in order to collect and sweepthe solid products (residues) along the floor of the conveyor housing 82and push them out of the exit snout 84 (FIG. 25).

The pyrolysis reactions occur while the feedstocks are being carried bythe rotary motion of the converter drum 66 up the inner periphery of thedrum. When the feedstocks overcome the angle of repose, they tumble downand have a component of forward motion due to the inclination of theaxis of the drum. As noted above, the inclination used is selected inaccordance with the feedstocks which are to be processed in order togive the required residence time in the converter for completion ofpyrolysis. A steeper angle shortens the residence time, because thematerials are carried up the side walls generally perpendicular to theaxis of rotation and tumble back down in a direction which isessentially vertical.

The gases consisting of methane, water vapor and other volatiles arereleased during pyrolysis of the materials and exit the outlet 87 to thedelivery pipe 42. This delivery pipe first enters the condenser 44 (seeFIGS. 33 to 35) which contains a bath of water to a level 222 abovewhich is a layer of oil to a level 220. The oil may be provided by thecondensed hydrocarbon gases which are delivered through the pipe 42.These gases flow under pressure, since the converter inner drum ispressurized (for example, to 5 PSIG as noted above). Baffles 224 directthe gases into the oil, since they are not long enough to extend belowthe water level 222. Longer baffles 224 direct the gases into the water.These baffles cause the gases to circulate and be cleaned of impuritiessuch as carbon particles, ash, calcium choride (the product of limeadded to the process in the converter drum plus chlorine fromchlorinated plastic such as vinyls, PCBs and the like). Also, sulfur andammonia are cleaned from the gases. The temperature in the bath ismaintained so as to condense aromatics, light and heavy oils withoutseparation and water vapors if a single condenser 44 is used. Ifmultiple condensers are used, upstream condensers which are of the fluidswept, rather than fluid bath type, are used to condense first heavyoils then light oils as temperatures decrease while the last condenser44 condenses aromatics and water vapor. The condenser 44 also functionsas a trap to prevent air from entering the converter(s). The oils whichare condensed are removed from the oil layer, for example, by valvedpipes or outlets which maintain the level 220. The water below the level224 may be circulated through heat exchangers or chillers and maintainedat the temperature for condensing aromatics and water vapor. Also,treatment facilities may be provided to maintain the water at a desiredpH level. As noted above, non-condensable gases may be used foroperating the burners to heat the converter 12. Alternatively, they maybe compressed and stored for later use in the process (for example, onstartup instead of propane) or for other purposes.

A fluid swept condenser is shown in FIGS. 36, 37 and 38. This condenserincludes baffles 228 which like the baffles 224 of the condenser 44 maybe connected to and supported by opposite side walls of the condenserhousing. Alternate ones of these baffles extend below the fluid level222 and cause the gas stream to sweep over the fluid. These condensersare identified by reference numeral 226 to differentiate them from thebaffles in the condensers 44.

A series of condensers 44 and 226 may be connected in tandem forprocessing condensing and cleaning the product gases from a plurality230 to 234 of converters as shown in FIG. 39 or from a single converter.The last condenser in the series is of the fluid bath type 44, while theremaining condensers 238, 240 and 242 are of the fluid swept type 226.These fluid swept condensers force the gases to expand and contract tocreate turbulence and cool as they sweep above the fluid. Thetemperatures of the various condensers may be gradually decreased. Forexample, the temperature of the first condenser 238 may be controlled tobe at 350° F., the second 240 at 290° F., and third 242 at about 230° F.and the last 44 at about 140° F. These temperatures are sufficient tokeep water vapors in suspension in the gas stream until the lastcondenser 44 is reached, while allowing light and heavy oils to condenseand also permitting the cleaning of the impurities in the gas stream.Since, the temperature of the last condenser 44 is about 140° F., mostlight aromatics and water vapors are condensed therein as discussedabove. In order to maintain the temperature of the condensers at thedesired temperature, cool water may be circulated via a chiller or heatexchanger 245 or from the public water supply to the lowest temperaturecondenser 44. Warmer water is withdrawn from the lower temperaturecondensers and then circulated to the higher temperature condensers,thus by maintaining only one temperature, all of the temperatures of thecondensers in the series may be maintained. As noted above, the oil maybe extracted by withdrawing it as it is separated from the gas stream ineach of the condensers as shown by the outlets 247 from each of thecondensers. The non-condensable gases are desirably compressed andstored in a tank 248 and then used in the heat source (burners) 26.

As noted above, the chimneys or flues 24 of the first converter 230 maybe connected via ducts 252 to the heat source 26 of the next successiveconverter 232. Similarly, the flue 24 of the converter 232 may beconnected to the next converter 234. The chimney of the last converter234 may be allowed to dissipate or may be connected to a burner to burnoff any combustibles therein. Alternatively, the chimney 24 may beconnected by another duct (not shown) to the burner 26 of the firstconverter 230.

The temperature within the converter drum in the converter 12 or in theplurality of converters 230, 232 and 234 is desirably maintained atapproximately 1200°. This temperature may be insufficient to reducecertain chlorinated hydrocarbons to within levels consideredenvironmentally safe. For example, PCBs may be contained in the residuefrom the discharge chute 30. To this end, a secondary converter 254which is operated at higher temperature may be used. The residue is fedinto the inlet end of a converter drum 258 of the secondary converter254 by a chute 256 (see FIG. 40). The converter 254 is similar in designto the converter 10 as described above in connection with FIGS. 1-38. Ithas an outer stationary drum 260, a casing 52 defining an oven chamber,and a drive shaft assembly 262. The auxiliary converter is supported onadditional members of the framework 48. The discharge from the secondaryconverter 254 is through a chute 30 and conveyor assembly 34 of the typedescribed in connection with FIGS. 1-38, and like parts are identifiedby reference numerals used in describing them in connection with FIGS.1-38. The burner of the secondary converter 254 desirably operates toheat the chamber containing the converter drum 258 to about 2400° F.which is believed sufficient to destroy the PCBs upon pyrolyzation. Thistemperature is only approximate and such temperatures are used which aresufficient to provide a residue which is within environmentally safelevels.

From the foregoing description, it will be apparent that there has beenprovided an improved pyrolytic conversion system. Variations andmodifications of the herein described system within the scope of theinvention will undoubtedly suggest themselves to those skilled in theart. Accordingly, the foregoing description should be taken asillustrative and not in a limiting sense.

I claim:
 1. A pyrolytic conversion system which comprises a plurality ofpyrolytic converters each for pyrolysis of solid hydrocarbon containingmaterials and each having means for heating said material by combustionof combustible gases and a flue for exhaust of said gases aftercombustion and after the transfer of heat therefrom, said convertershaving separate inlets for introducing said materials therein andseparate outlets for product gases produced upon pyrolysis thereof,common means connected to the product gases outlets of said convertersfor cleaning and condensing said product gases and providing saidproduct gases to the heating means of said converters for combustiontherein, and means for connecting the flue of at least one of saidplurality of converters to the heating means of another of saidplurality of converters for preheating said heating means.
 2. The systemaccording to claim 1 wherein said means for cleaning and condensing saidproduct gases comprises a plurality of fluid bath and fluid sweptcondensers and means connecting said condensers in tandem for the flowof said product gases successively therethrough.
 3. The system accordingto claim 2 wherein a last of said plurality of condensers in the path ofsaid gases from said converters has baffles therein for directing saidgases into the bath therein, and others of said condensers have bafflesfor directing the gases across the surface of the bath therein.
 4. Thesystem according to claim 2 further comprising means for maintaining thebaths in said condensers at successively lower temperatures, the highestof said temperatures being in one of said condensers through which saidgases from said converters first pass, the temperature in the last ofsaid tandem connected condensers being below the condensationtemperature of water vapor.
 5. The system according to claim 4 whereinthe last of said temperatures is about 140° F.